VWoA sends the letters out. If you've moved since your purchase, you may not get it. You can check
https://www.nhtsa.gov/recalls to see if your VIN is included in the campaign.
I just got mine back (airbox mods only) and took a short drive (have to start dinner) and here's the major things I noticed.
Start/Stop is smoother, it used to clunk when stopping and vibrates when starting. Most of that is gone now.
Accel is smoother in D but still laggy (I mostly drive in S)
Maybe related, maybe because adapations are reset? Dunno, I can only speculate.
I've picked up some DSG farts at a much lower RPM, previously I'd only get them over 5k. Got a few small farts around 4200rpm now and there is a bit more burble. I doubt it's related, but I got more farts on this drive home than in the months since I changed to the TCR suitcase.
Exhaust doesn't sound the same, it's lower in tone and seems to have more of a growl.